Referring to FIG. 1, an existing 3rd Generation Partnership Project (3GPP) radio network is divided into a 3GPP radio access network (RAN) and a core network (CN).
The 3GPP RAN is further classified into three types as follows.
GSM edge radio access network (GERAN): 2G/2.5G access network, collectively referred to as 2G access network below, and including a base transceiver station (BTS) and a base station controller (BSC).
Universal terrestrial radio access network (UTRAN): 3G access network, including a node B (NodeB) and a radio network controller (RNC).
Evolved UMTS terrestrial radio access network (EUTRAN): also known as future long term evolution (LTE) access network, including an evolved node B (eNodeB, and eNB for short below).
The above three RANs are all configured to implement functions related to radio services, and meanwhile realize security capability negotiation with terminals.
A 2G/3G core network is further divided into a circuit-switched (CS) domain and a packet-switched (PS) domain. For ease of illustration, CS-related entities are omitted, and only the PS domain remains. The PS domain performs data service exchange and routing with external packet-based networks beforehand, and includes a serving GPRS support node (SGSN) and a gateway GPRS support node (GGSN). The SGSN is mainly configured to realize route-forwarding, mobility management, session management, and user authentication, and the GGSN is mainly configured to realize the connection with the external packet-based networks, and also implement data transmission on the user plane.
A future evolved core network is also referred to as a system architecture evolution (SAE), including entities such as a mobility management entity (MME) and SAE gateway (SAE GW)/packet data network gateway (PDN GW)/home subscriber server (HSS). Similar to the SGSN, the MME is mainly configured to realize mobility management and user authentication. The SAE GW/PDN GW serves as anchor points on the user plane between different access systems. The HSS is mainly configured to store user subscription data.
In the 2G network, the SGSN performs the security capability algorithm negotiation between the signaling plane and the user plane. In the 3G network, the RNC performs the security capability algorithm negotiation between the signaling plane and the user plane. In the evolved network LTE/SAE, as the RNC/SGSN does not exist, the MME performs the non-access signaling (NAS) algorithm negotiation, and the eNB performs the radio resource control (RRC)/user plane (UP) algorithm negotiation.
When a user is handed over from a 2G/3G network (2G/3G) to an LTE network, or from an LTE to a 2G/3G network, as the entities responsible for the security capability negotiation change and the security capabilities thereof may be different, the security capability negotiation needs to be re-performed. Here, the security capability negotiation means encryption algorithm for the 2G network, means integrity protection algorithm and encryption algorithm for the 3G network, and means NAS algorithm (encryption algorithm and integrity protection algorithm), RRC algorithm (encryption algorithm and integrity protection algorithm), and UP algorithm (encryption algorithm) for the LTE network.
Particularly, during the handover from the LTE network to the 2G/3G network, a user equipment (UE) sends its own GERAN (encryption algorithm)/UTRAN security capability (encryption algorithm and integrity protection algorithm) carried in an initial Layer 3 message to the MME. The MME then sends the capabilities of the UE to the SGSN. The SGSN selects and sends the corresponding GERAN/UTRAN security capability algorithm to the UE through the MME. During the handover from the LTE to 2G, the SGSN selects the security capability algorithm. However, during the handover from the LTE to 3G, according to the above description about the 3G network, the RNC, instead of the SGSN, selects the security capability algorithm; otherwise, the SGSN has to introduce a new requirement of selecting the security capability algorithm. Meanwhile, the SGSN must know the security capability of the RNC in a certain manner, and then sends the selected algorithm to the RNC, so that additional interaction between the SGSN and the RNC needs to be constructed.
During the handover from the 2G/3G to the LTE, the SGSN queries the UE for the NAS (encryption algorithm and integrity protection algorithm)/UP (encryption algorithm)/RRC (encryption algorithm and integrity protection algorithm) security capability. During the handover from the 2G/3G to the LTE, the SGSN sends the capabilities of the UE to the MME. Then, the MME selects and sends all the NAS/RRC/UP security capability algorithms to the UE through the SGSN.
In the implementation of the present invention, it is found in the prior art that, as the MME selects all the NAS/RRC/UP security capability algorithms, the MME must know the security capability of the corresponding eNB in a certain manner (for example, by configuring or extending interactive messages with the eNB), thus resulting in an inflexible configuration and a complicated process flow.